The clinicopathologic features of four infants with undiagnosed total anomalous pulmonary venous return who died suddenly and unexpectedly are presented. Two infants were found dead in their beds and two collapsed following very non-specific episodes of mild tachypnoea and tachycardia, respectively. Pulmonary venous blood drained via a common channel to the left innominate vein, the superior vena cava, the inferior vena cava at the junction of the hepatic vein and the supradiaphragmatic portion of the inferior vena cava. All cases demonstrated right atrial and ventricular hypertrophy and in one case there was associated hypoplastic left heart syndrome. Although those mechanisms responsible for sudden infant death syndrome could not definitely be excluded in two cases, the presence of anomalous pulmonary drainage with significant right-sided cardiac cardiac hypertrophy in each patient strongly suggests a contributing role for the vascular malformation in the aetiology of sudden unexpected death. The importance of careful in situ dissection of the major vessels in all cases of paediatric sudden death is emphasised, particularly in the presence of other congenital cardiac anomalies.